It's a season of tuition uncertainty in the state: The price of a year at California State University could soon rise again by hundreds of dollars - or swing back to what it was a year ago, with rebates for students.

It all depends on what voters do about Proposition 30, a nail-biter tax measure on the November ballot that would bring a windfall to state coffers if approved, or trigger a $250 million cut each to the CSU and the University of California if defeated.

On Wednesday, the CSU trustees, meeting in Long Beach, took the unprecedented step of approving both a tuition increase and a tuition rollback on the same day - each scenario dependent on what happens at the ballot box on Nov. 6.

If Prop. 30 fails, tuition would rise by 5 percent, beginning in January. Undergraduate tuition would rise by $300 a year to $6,270, up from $5,970. With the mandatory campus fee that averages more than $1,000, the price of a year at CSU - excluding room, board and books - would be about $7,317.

Students would see no immediate increase to their financial aid, CSU said. Tuition rates for graduate students, nonresidents, and students earning a credential would also rise.

If Prop. 30 wins, the state would add $125 million to CSU's budget in 2013-14 - but only if the university rescinds a tuition increase that took effect this semester.

As a result, the trustees agreed that if Prop. 30 wins, the undergraduate price tag would drop by 9.1 percent, to last year's $5,472. Tuition for other students - graduates, nonresidents and those in a credential program - would also drop. Mandatory campus fees would not be affected.

Although CSU officials anxiously hope Prop. 30 will pass, Chancellor Charles Reed acknowledged that the tuition rollback "is a nightmare for us. We've got to get started now in order to do the rebate and have that ready right away - we can't do it in December," he told the trustees. "It would be too late."

It's expected that refunds would go only to students who are graduating or leaving CSU. Those staying on would likely see their tuition bill - or their financial aid - reduced by $249 in the spring, said Mike Uhlenkamp, the university's spokesman.

The rollback would be a nightmare for CSU for another reason besides the logistics of refunds:

It would put a $132 million hole in CSU's current budget, so the university would take $50 million from its extension programs to help bridge the gap until the new money authorized by Prop. 30 arrived next year.

UC, which did not raise tuition for the first time since 2006, is making no plans for refunds.

The Department of Finance estimates that Prop. 30, placed on the ballot by Gov. Jerry Brown, would raise up to $9 billion a year for state services, including public education. It would raise the state sales tax by a penny for every $4 spent, expiring after four years, and boost income tax for individuals earning at least $250,000 a year. The increase would last seven years.

A competing tax measure, Proposition 38, is largely financed by attorney Molly Munger and would raise income taxes on most income levels for 12 years. Expected to raise about $10 billion a year, the money would pay down bond debt for four years, and shift to elementary and secondary schools after that.

If Prop. 38 passes, it's possible that budgets for California universities would still be cut by $250 million, and those for community colleges by $338 million. State law says only that the cuts would be triggered by the defeat of Prop. 30.

In addition to the tuition increase, CSU trustees approved other cuts to cover a $250 million hole, including increased employee contributions to health-care.